I have a Airport Time Capsule running my WiFi network at home, but have a bit of a weaker area near my bedroom (upstairs) so got an Airport Express to help it out. I set it up using Airport Utility to extend the network, and that seems good so far. It's connecting wirelessly, for now, which I'm comfortable with (not concerned with actual downstream speed, at the moment).
Unfortunately, the Airport Express seems to have picked a poor channel. I used NetSpot to see how its coverage was, and the answer was more-or-less terrible: while the Time Capsule still is in the green-ish (~40-50 db) range even in the 'poor' areas, the Airport Express is twenty feet away and still no better than that.
I notice from the channels that the Express is on the very overused near me Channel 11, while the main Time Capsule is on Channel 1 (both for 2.5Ghz, which is the one I'd expect it to mostly use). Is there a way to change that? I go into Airport Utility, and I can change the channel the Time Capsule is using (under Wireless Options), but that setting isn't there for the Airport Express. My understanding of how a Wi-Fi Extender should work is that it should not use the same channel; so I don't see why Apple would force this to automatic. Is it so (forced) or is there a way to work around this? (Also, the 5Ghz channel is identical for both devices, which again I'd think is bad.)
I have both Mac and Windows computers available, if that's relevant.